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The Arabidopsis plastid-signalling mutant gun1 (genomes uncoupled1) shows altered sensitivity to sucrose and abscisic acid and alterations in early seedling development.

Cottage A, Mott EK, Kempster JA, Gray JC - J. Exp. Bot. (2010)

Bottom Line: Norflurazon and lincomycin, which induce retrograde signalling, further decreased the anthocyanin content of sucrose-treated seedlings, and altered the temporal pattern of anthocyanin accumulation.Lincomycin treatment altered the spatial pattern of sucrose-induced anthocyanin accumulation, suggesting that plastids provide information for the regulation of anthocyanin biosynthesis in Arabidopsis seedlings.Growth and development of gun1 seedlings was more sensitive to exogenous 2% sucrose than wild-type seedlings and, in the presence of lincomycin, cotyledon expansion was enhanced in gun1 seedlings compared to the wild type. gun1 seedlings were more sensitive than wild-type seedlings to the inhibition of seedling growth and development by abscisic acid.

View Article: PubMed Central - PubMed

Affiliation: Department of Plant Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EA, UK.

ABSTRACT
Developing seedlings of the Arabidopsis gun1 (genomes uncoupled1) mutant, which is defective in retrograde plastid-to-nucleus signalling, show several previously unrecognized mutant phenotypes. gun1 seedlings accumulated less anthocyanin than wild-type seedlings when grown in the presence of 2% (w/v) sucrose, due to lower amounts of transcripts of early anthocyanin biosynthesis genes in gun1. Norflurazon and lincomycin, which induce retrograde signalling, further decreased the anthocyanin content of sucrose-treated seedlings, and altered the temporal pattern of anthocyanin accumulation. Lincomycin treatment altered the spatial pattern of sucrose-induced anthocyanin accumulation, suggesting that plastids provide information for the regulation of anthocyanin biosynthesis in Arabidopsis seedlings. The temporal pattern of accumulation of LHCB1 transcripts differed between wild-type and gun1 seedlings, and gun1 seedlings were more sensitive to sucrose suppression of LHCB1 transcript accumulation than wild-type seedlings. Growth and development of gun1 seedlings was more sensitive to exogenous 2% sucrose than wild-type seedlings and, in the presence of lincomycin, cotyledon expansion was enhanced in gun1 seedlings compared to the wild type. gun1 seedlings were more sensitive than wild-type seedlings to the inhibition of seedling growth and development by abscisic acid. These observations clearly implicate GUN1 and plastid signalling in the regulation of seedling development and anthocyanin biosynthesis, and indicate a complex interplay between sucrose and plastid signalling pathways.

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Effect of ABA on development of wild-type and gun1 seedlings. Percentage of 9-d-old seedlings having reached the growth stages defined by Boyes et al. (2001); 0.1, seed imbibition; 0.5, radicle emergence; 0.7, hypocotyl and cotyledon emergence; 1.0, cotyledons fully open. Three replicate samples of 100 wild-type (Col-0) and gun1 seeds were sown on 0.5× MS-agar medium ±0.5 μM ABA, stratified for 48 h in the dark at 4 °C and then transferred to continuous illumination (120 μmol m−2 s−1) at 22 °C. The number of seedlings reaching, or passing, each growth stage was counted 9 d after transfer to light at 22 °C. Results are expressed as mean ±standard error for three replicate samples.
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fig9: Effect of ABA on development of wild-type and gun1 seedlings. Percentage of 9-d-old seedlings having reached the growth stages defined by Boyes et al. (2001); 0.1, seed imbibition; 0.5, radicle emergence; 0.7, hypocotyl and cotyledon emergence; 1.0, cotyledons fully open. Three replicate samples of 100 wild-type (Col-0) and gun1 seeds were sown on 0.5× MS-agar medium ±0.5 μM ABA, stratified for 48 h in the dark at 4 °C and then transferred to continuous illumination (120 μmol m−2 s−1) at 22 °C. The number of seedlings reaching, or passing, each growth stage was counted 9 d after transfer to light at 22 °C. Results are expressed as mean ±standard error for three replicate samples.

Mentions: Screens for mutants showing alterations in sucrose effects on seedling development have largely yielded sugar-insensitive mutants, many of which are also ABA insensitive, establishing links between sugar and ABA signalling. Far fewer sugar-hypersensitive mutants have been identified (reviewed in Leon and Sheen, 2003), and few of these are also hypersensitive to ABA. To examine the possible effect of ABA on seed germination and seedling development, gun1 and wild-type seeds were sown on a range of ABA concentrations (0–25 μM) and seedling growth monitored over 21 d. The greatest difference in seedling development between wild-type and gun1 seedlings was seen in 9-d-old seedlings grown on 0.5 μM ABA; only 11% of gun1 seedlings had reached the stage of cotyledon emergence whereas 80% of wild-type seedlings had reached this stage (Fig. 9). gun1 can therefore be considered to have an ABA-hypersensitive phenotype.


The Arabidopsis plastid-signalling mutant gun1 (genomes uncoupled1) shows altered sensitivity to sucrose and abscisic acid and alterations in early seedling development.

Cottage A, Mott EK, Kempster JA, Gray JC - J. Exp. Bot. (2010)

Effect of ABA on development of wild-type and gun1 seedlings. Percentage of 9-d-old seedlings having reached the growth stages defined by Boyes et al. (2001); 0.1, seed imbibition; 0.5, radicle emergence; 0.7, hypocotyl and cotyledon emergence; 1.0, cotyledons fully open. Three replicate samples of 100 wild-type (Col-0) and gun1 seeds were sown on 0.5× MS-agar medium ±0.5 μM ABA, stratified for 48 h in the dark at 4 °C and then transferred to continuous illumination (120 μmol m−2 s−1) at 22 °C. The number of seedlings reaching, or passing, each growth stage was counted 9 d after transfer to light at 22 °C. Results are expressed as mean ±standard error for three replicate samples.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC2921207&req=5

fig9: Effect of ABA on development of wild-type and gun1 seedlings. Percentage of 9-d-old seedlings having reached the growth stages defined by Boyes et al. (2001); 0.1, seed imbibition; 0.5, radicle emergence; 0.7, hypocotyl and cotyledon emergence; 1.0, cotyledons fully open. Three replicate samples of 100 wild-type (Col-0) and gun1 seeds were sown on 0.5× MS-agar medium ±0.5 μM ABA, stratified for 48 h in the dark at 4 °C and then transferred to continuous illumination (120 μmol m−2 s−1) at 22 °C. The number of seedlings reaching, or passing, each growth stage was counted 9 d after transfer to light at 22 °C. Results are expressed as mean ±standard error for three replicate samples.
Mentions: Screens for mutants showing alterations in sucrose effects on seedling development have largely yielded sugar-insensitive mutants, many of which are also ABA insensitive, establishing links between sugar and ABA signalling. Far fewer sugar-hypersensitive mutants have been identified (reviewed in Leon and Sheen, 2003), and few of these are also hypersensitive to ABA. To examine the possible effect of ABA on seed germination and seedling development, gun1 and wild-type seeds were sown on a range of ABA concentrations (0–25 μM) and seedling growth monitored over 21 d. The greatest difference in seedling development between wild-type and gun1 seedlings was seen in 9-d-old seedlings grown on 0.5 μM ABA; only 11% of gun1 seedlings had reached the stage of cotyledon emergence whereas 80% of wild-type seedlings had reached this stage (Fig. 9). gun1 can therefore be considered to have an ABA-hypersensitive phenotype.

Bottom Line: Norflurazon and lincomycin, which induce retrograde signalling, further decreased the anthocyanin content of sucrose-treated seedlings, and altered the temporal pattern of anthocyanin accumulation.Lincomycin treatment altered the spatial pattern of sucrose-induced anthocyanin accumulation, suggesting that plastids provide information for the regulation of anthocyanin biosynthesis in Arabidopsis seedlings.Growth and development of gun1 seedlings was more sensitive to exogenous 2% sucrose than wild-type seedlings and, in the presence of lincomycin, cotyledon expansion was enhanced in gun1 seedlings compared to the wild type. gun1 seedlings were more sensitive than wild-type seedlings to the inhibition of seedling growth and development by abscisic acid.

View Article: PubMed Central - PubMed

Affiliation: Department of Plant Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EA, UK.

ABSTRACT
Developing seedlings of the Arabidopsis gun1 (genomes uncoupled1) mutant, which is defective in retrograde plastid-to-nucleus signalling, show several previously unrecognized mutant phenotypes. gun1 seedlings accumulated less anthocyanin than wild-type seedlings when grown in the presence of 2% (w/v) sucrose, due to lower amounts of transcripts of early anthocyanin biosynthesis genes in gun1. Norflurazon and lincomycin, which induce retrograde signalling, further decreased the anthocyanin content of sucrose-treated seedlings, and altered the temporal pattern of anthocyanin accumulation. Lincomycin treatment altered the spatial pattern of sucrose-induced anthocyanin accumulation, suggesting that plastids provide information for the regulation of anthocyanin biosynthesis in Arabidopsis seedlings. The temporal pattern of accumulation of LHCB1 transcripts differed between wild-type and gun1 seedlings, and gun1 seedlings were more sensitive to sucrose suppression of LHCB1 transcript accumulation than wild-type seedlings. Growth and development of gun1 seedlings was more sensitive to exogenous 2% sucrose than wild-type seedlings and, in the presence of lincomycin, cotyledon expansion was enhanced in gun1 seedlings compared to the wild type. gun1 seedlings were more sensitive than wild-type seedlings to the inhibition of seedling growth and development by abscisic acid. These observations clearly implicate GUN1 and plastid signalling in the regulation of seedling development and anthocyanin biosynthesis, and indicate a complex interplay between sucrose and plastid signalling pathways.

Show MeSH
Related in: MedlinePlus